1. Field of the Invention
This invention relates generally to a fluid control valve and, more particularly, to a proportional, variable force solenoid control valve that includes improvements over existing control valves, such as a flux shunt pole piece and a specialized crimped housing.
2. Discussion of the Related Art
Modern vehicles generally employ an automatic transmission controller that includes several solenoid operated fluid control valves that independently act to control the pressure of the transmission fluid in the vehicle's transmission to operate various components of the transmission. For example, solenoid operated fluid control valves are known that use transmission fluid pressure to engage and disengage the transmission clutch in response to an electrical input signal supplied to the solenoid. One particular type of solenoid control valve is referred to as a variable force solenoid control valve. Typically, variable force solenoid control valves comprise fluid control components including a spool valve having a stem and two radially extending lobes or lands. The spool valve is movably confined within a valve body to create flow restrictions for pressure regulation. Fluid passages are provided in the valve body which communicate with the various surfaces of the spool valve. Fluid at an inlet pressure is delivered to a flow restriction provided between the two spool valve lands. The flow restriction enables the fluid pressure to be reduced to a desired outlet control pressure.
U.S. Pat. No. 5,277,399 issued to McCabe discloses a solenoid operated fluid control valve for use in a control system of an automatic transmission of a vehicle. The control valve includes an electromagnetic coil positioned within a housing and a spool valve positioned within a valve body. An armature is axially positioned within the coil and an armature spring biases the armature towards the spool valve when the coil is not energized. The spool valve includes an internal chamber and a series of sealing lands that selectively seal a supply port and a control port within the valve body. A pole piece is threadably engaged within the housing, and controls a working air gap between the pole piece and the armature. By energizing the coil, the pressure within the bore and the valve body is controlled.
Although the variable force solenoid control valves known in the prior art have generally been successful in meeting the demands of the industry, these control valves can be further improved upon. As the controllers become more sophisticated, it is necessary that the solenoid operated control valves also include advancements and improvements over the state of the art. In this regard, it becomes important to increase the operating efficiency, reduce the cost, reduce the weight, reduce the complexity, etc. of the existing control valves. Therefore, advancements in size, part reduction, component simplification, etc. of the known control valves is advantageous.
It is an object of the present invention to provide an improved variable force control valve for use in an automatic controller.